Renal Accumulation and Hemocyte-Mediated Internalization After Acute Exposure to Injected Polyethylene Terephthalate Nanoplastics (PET-NPs) in the Freshwater Gastropod Pomacea canaliculata.

The increasing fragmentation of plastic debris into nanosized particles represents a threat to freshwater ecosystems, yet the biological effects of nanoplastics (NPs) on freshwater invertebrates remain poorly understood. This study investigated tissue distribution, cellular effects and immune responses following acute exposure to polyethylene terephthalate nanoplastics (PET-NPs) in the freshwater gastropod Pomacea canaliculata, a species of high ecological relevance and physiological resilience. Adult snails were injected with PET-NPs at 5 or 10 mg/L and sampled after 24 and 72 h. PET-NPs accumulation in the anterior and posterior kidneys was assessed by fluorescence imaging and tissue morphology was evaluated. Stress- and inflammation-related genes (Pc-Heat Shock Protein (HSP)70, Pc-HSP90 and Pc-Allograft inflammatory factor 1) expression was quantified by RT-qPCR. PET-NPs uptake and phagocytic activity were analyzed in circulating hemocytes in vivo and ex vivo. PET-NPs were accumulated in renal tissues, persisting up to 72 h without histopathological alterations. Gene expression analyses revealed non-linear and dose/time-dependent responses. Hemocytes of different morphologies internalized PET-NPs in a dose-dependent manner and showed intercellular particle transfer. Overall, acute PET-NP exposure determines rapid immune handling and tissue sequestration with limited short-term physiological impact, underscoring the potential involvement of immune processes in NPs fate and highlighting the need for chronic exposure studies.